Effect of galvannealed coating on corona bond strength of resistance spot welding

The effect of galvannealed (GA) coating on the corona bond strengths of resistance spot welding joints was investigated. A cross tensile test was performed with removal of the nugget, using GA steel sheets and steel sheets whose coating had been removed via pickling. The maximum load with coating was lower than that without coating. When the nugget diameter was small (3√t, t: sheet thickness), GA coating reduced the corona bond strength (MPa). In contrast, when the nugget diameter was large (5√t), GA coating did not change the corona bond strength but reduced the corona bond area.